The present invention relates to an engine driven generator set system that does not exert any roll torque on its mounting structure. More particularly, the present invention relates to reduction or elimination of vibratory roll torques of an engine driven generator set system wherein the rotor and the stator are rotated in opposite directions.
The present invention applies to generator sets having rotating parts which are subject to vibratory roll torques caused by transient or cyclic electrical loads, starting torques and shutdown torques, cyclic combustion torques, etc. The present invention also applies to various applications where generators/alternators are used; for example, alternators for automobile engines, auxiliary power units for hybrid electric vehicles, etc.
Engine driven generator set systems have been commercially manufactured and marketed for several decades. An engine driven generator set system that imparts no vibratory torque on its mounting structure is desirable because vibrations cause mechanical damage, human discomfort, etc.
In engine driven generator set systems, particularly piston engine generator systems, vibrations occur in the engine from various causes. One major cause of these vibrations is roll torque. The vibratory roll torque is caused by the successive firing of the cylinders. The successive explosions in the cylinders, which push the pistons down and meanwhile turn the crankshaft, act also on each of the cylinders and the engine which results in net roll torques being transmitted to the engine supporting structure which causes vibration.
The aforementioned roll torque can be reduced by making engines with many cylinders. However, many engine driven generator sets are required to be small size, light weight, and low cost so that the engine driven generator set is often made with a few cylinders.
To deal with the above vibrations, a single cylinder engine-generator set is disclosed by Canadian Patent No. 920454, issued on Feb. 6, 1974, to Victor Heron. In the Canadian patent, a rotor is mounted on an end of a crankshaft of the engine, and a pair of counter-rotating balance shafts with fly wheels, which are disposed side-by-side and parallel to the crankshaft of the engine, are driven by two gears which are coupled with a gear on the crankshaft. A plurality of flywheels and counterweights are disposed on the balance shafts and the crankshaft, respectively. When the engine and generator are running, the net angular momentum of its rotating parts are zero resulting in no net roll torque. Accordingly, sudden angular accelerations caused by cylinder firing cause no movement in the supporting structure of the engine and generator. However, the balance shafts and flywheels can result in unacceptably large and costly generator sets.
The present invention relates to a generator set having no net roll torque which can be optimized for very low noise, small package size, low cost, and/or increased power density requirements.